The current DVB Digital television standard defines broadcast of audio, video and additional data on a stream. From this additional content, the interactive digital TV middleware MHP (Multimedia Home Platform) is able to extract several tables defined by the DVB SI (Section Information) standard relating to signaling information. Amongst these tables, the Event Information Table (EIT) contains data about the Events (the programs) broadcast on a specific Service (the channel). These data can then be browsed by means of specific software, called an Electronic Program Guide (EPG), which displays a list of Services (the channels) and their associated Events (the programs). However, the end-user is limited to browsing data coming from the stream only (that is a terrestrial, satellite or cable signal) and from no other source.
The DVB SI norm states that the EIT provides, amongst others, the name of the event, the start time of the event, the duration of the event, a locator, which is special information for the receiver (the Set Top Box or STB) to tune to the right Service.
Future developments of digital TV will probably provide several complementary sources linked to an Event: genuine DVB MPEG2 (Moving Picture Expert Group 2) streamed data (broadcast on a satellite, terrestrial or cable signal) and, for instance, an additional MPEG4 (Moving Picture Expert Group 4) preview stream coming from the Internet.
For such an application (MPEG4 preview stream coming from the Internet), the SDP/SAP protocols (Service Description Protocol/Service Announcement Protocol) seem to suit well, for they are designed to allow participation to multimedia conferences on the Internet. An end-user uses the SAP to register to an MPEG4 video announcer and is notified of the parameters of the video session thanks to the SDP. Therefore, the user needs several parameters, such as the name of the video, the start and end time of the video, the IP address of the MPEG4 video server and the number of the port on which the video is played.
Watching an SDP/SAP Internet-distributed MPEG4 preview of a broadcast MPEG2 Event would impose the merging of the SDP/SAP information (IP address and port) with the genuine DVB SI Event data, while complying with the DVB SI standard (and the EIT structure).